Continuous power supplying is very important to many electronic equipments, especially to communication systems, internet servers etc. When the unexpected event results in power supply interruption, the backup power has to be activated by protecting circuit. Therefore, the power supplying for protecting circuit is especially important. At present, the combination of transient voltage suppressor (TVS) and fuse is used for protecting the circuit when the power supply is reversed. But the fuse is broken after once protection, and it must be replaced for using next time. The maintenance is inconvenience.